LMP2021 datasheet(24/42 Pages) TI2

24 / 42 page

0.0

0.5

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-12 -10

-8

-6

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-2

DIFFERENTIAL INPUT (mV)

C001

LMP2021, LMP2022

SNOSAY9G – SEPTEMBER 2008 – REVISED FEBRUARY 2016

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Product Folder Links: LMP2021 LMP2022

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Typical Application (continued)

Bridge sensor measurements are usually done up to 10s of Hz. Placing a 300 Hz filter on the LMP2022 helps

removing the higher frequency noise from this circuit. This filter is created by placing two capacitors in the

feedback path of the LMP2022 amplifiers.

This amplified signal is then fed into the ADC161S626. The ADC161S626 is a 16-bit, 50 kSPS to 250 kSPS 5V

ADC. In order to utilize the maximum number of bits of the ADC161S626 in this configuration, a 2.5V reference

voltage is used. This 2.5V reference is also used to power the bridge sensor and the inverting input of the ADC.

Using the same voltage source for these three points helps reducing the total system error by eliminating error

due to source variations.

With this system, the output signal of the bridge sensor which can be up to ±13.3 mV and is accurately scaled to

the full scale range of the ADC and then digitized for further processing. The LMP202x introduced minimal error

to the system and improved the signal quality by removing common mode signals and high frequency noise.

8.2.3 Application Curve

Figure 47. Single Ended Output Results for Bridge Circuit

9 Power Supply Recommendations

The LMP202x is specified for operation from 2.2 V to 5.5 V (±1.1 V to ±2.75 V) over a –40°C to +125°C

temperature range. Parameters that can exhibit significant variance with regard to operating voltage or

temperature are presented in the Typical Characteristics.

CAUTION

Supply voltages larger than 6 V can permanently damage the device.

10 Layout

10.1 Layout Guidelines

For best operational performance of the device, use good printed circuit board (PCB) layout practices, including:

•

Noise can propagate into analog circuitry through the power pins of the circuit as a whole and op amp itself.

Bypass capacitors are used to reduce the coupled noise by providing low-impedance power sources local to

the analog circuitry.

•

Connect low-ESR, 0.1-

μF ceramic bypass capacitors between each supply pin and ground, placed as close

to the device as possible. A single bypass capacitor from V+ to ground is applicable for single supply

applications.

•

Separate grounding for analog and digital portions of circuitry is one of the simplest and most-effective

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